LVM磁盘阵列技术
· 什么是LVM
LVM（Logical Volume Manager，逻辑卷管理器），动态调整分区大小
LVM是Linux系统用于对硬盘分区进行管理的一种机制，理论性较强
LVM技术是在硬盘分区和文件系统之间添加了一个逻辑层，它提供了一个抽象的卷组，可以把多块硬盘进行卷组合并。不必关心物理硬盘设备的底层架构和布局，就可以实现对硬盘分区的动态调整
逻辑卷管理器的技术结构
逻辑卷管理器使用流程图
· 相关LVM命令
常用的LVM部署命令
· LVM部署
部署逻辑卷
添加两块硬盘设备
1.让新添加的两块硬盘设备支持LVM
[root@xiudaochengxian ~]# ls -l /dev/sd* #查看硬盘设备
brw-rw----. 1 root disk 8, 0 Nov 1 16:34 /dev/sda
brw-rw----. 1 root disk 8, 1 Nov 1 16:34 /dev/sda1
brw-rw----. 1 root disk 8, 2 Nov 1 16:34 /dev/sda2
brw-rw----. 1 root disk 8, 3 Nov 1 16:34 /dev/sda3
brw-rw----. 1 root disk 8, 16 Nov 1 16:34 /dev/sdb
brw-rw----. 1 root disk 8, 32 Nov 1 16:34 /dev/sdc
[root@xiudaochengxian ~]# pvcreate /dev/sdb #使新硬盘支持LVM
Physical volume "/dev/sdb" successfully created.
[root@xiudaochengxian ~]# pvcreate /dev/sdc
Physical volume "/dev/sdc" successfully created.
2.将创建的两块硬盘设备加入卷组里
[root@xiudaochengxian ~]# vgcreate shuaige /dev/sdb /dev/sdc #将两块硬盘加入卷组（shuaige）里
Volume group "shuaige" successfully created
3.创建逻辑卷
[root@xiudaochengxian ~]# lvcreate -n haha -l 100 shuaige #切割出一个约为400MB的逻辑卷设备
Logical volume "haha" created.
[root@xiudaochengxian ~]# lvdisplay #查看状态
--- Logical volume ---
LV Path /dev/shuaige/haha
LV Name haha
VG Name shuaige
LV UUID SKbcGd-DcP1-WJB9-pgQt-mt9e-ORgc-ZeA7xs
LV Write Access read/write
LV Creation host, time xiudaochengxian, 2021-11-01 16:42:57 +0800
LV Status available
# open 0
LV Size 400.00 MiB
Current LE 100
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:0
4.格式化生成好的逻辑卷，然后挂载使用
Linux系统会把LVM中的逻辑卷设备存放在/dev设备目录中（实际上就是个快捷方式），同时会以卷组的名称来建立一个目录，其中保存了逻辑卷的设备映射文件（即/dev/卷组名称/逻辑卷名称）
例：/dev/shuaige/haha
[root@xiudaochengxian ~]# mkfs.ext4 /dev/shuaige/haha #格式化
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
102400 inodes, 409600 blocks
20480 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=34078720
50 block groups
8192 blocks per group, 8192 fragments per group
2048 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409
Allocating group tables: done
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done
[root@xiudaochengxian ~]# mkdir /haha #创建目录
[root@xiudaochengxian ~]# vim /etc/fstab #写入配置文件，永久生效
13 /dev/shuaige/haha /haha ext4 defaults 0 0
[root@xiudaochengxian ~]# mount -a #挂载
[root@xiudaochengxian ~]# df -h #查看挂载情况
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 17G 3.5G 14G 21% /
devtmpfs 1.9G 0 1.9G 0% /dev
tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs 1.9G 13M 1.9G 1% /run
tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/sr0 4.2G 4.2G 0 100% /media/cdrom
/dev/sda1 1014M 165M 850M 17% /boot
tmpfs 378M 4.0K 378M 1% /run/user/42
tmpfs 378M 20K 378M 1% /run/user/0
/dev/mapper/shuaige-haha 380M 2.3M 354M 1% /haha
注： 如果使用了逻辑卷管理器，则不建议用XFS文件系统
因为XFS文件系统自身就可以使用xfs_growfs命令进行磁盘扩容
在实测阶段发现，在有一些服务器上，XFS与LVM的兼容性并不好
※ 扩容逻辑卷（红帽考试内容之一）
注： 扩容前请一定要记得卸载设备和挂载点的关联
1.卸载文件系统
[root@xiudaochengxian ~]# umount /haha
2.扩容
[root@xiudaochengxian ~]# lvextend -L 800M /dev/shuaige/haha #扩容800MB
Size of logical volume shuaige/haha changed from 400.00 MiB (100 extents) to 800.00 MiB (200 extents).
Logical volume shuaige/haha successfully resized.
3.检查硬盘的完整性，确认目录结构、内容和文件内容没有丢失，一般情况下是要没有报错，均为正常情况
[root@xiudaochengxian ~]# e2fsck -f /dev/shuaige/haha
e2fsck 1.42.9 (28-Dec-2013)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/shuaige/haha: 11/102400 files (0.0% non-contiguous), 23456/409600 blocks
4.通知文件系统发生变化，重置设备在系统中的容量（手动进行同步系统内核还没有同步到这部分新修改的信息）
[root@xiudaochengxian ~]# resize2fs /dev/shuaige/haha
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/shuaige/haha to 819200 (1k) blocks.
The filesystem on /dev/shuaige/haha is now 819200 blocks long.
5.重新挂载硬盘设备并查看挂载状态
[root@xiudaochengxian ~]# mount -a
[root@xiudaochengxian ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 17G 3.5G 14G 21% /
devtmpfs 1.9G 0 1.9G 0% /dev
tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs 1.9G 13M 1.9G 1% /run
tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/sr0 4.2G 4.2G 0 100% /media/cdrom
/dev/sda1 1014M 165M 850M 17% /boot
tmpfs 378M 4.0K 378M 1% /run/user/42
tmpfs 378M 24K 378M 1% /run/user/0
/dev/mapper/shuaige-haha 767M 2.5M 721M 1% /haha
相关命令：
缩小逻辑卷
1.卸载文件系统
[root@xiudaochengxian ~]# umount /haha
2.检查文件系统的完整性
[root@xiudaochengxian ~]# e2fsck -f /dev/shuaige/haha
e2fsck 1.42.9 (28-Dec-2013)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/shuaige/haha: 11/204800 files (0.0% non-contiguous), 36617/819200 blocks
3.通知文件系统缩小
[root@xiudaochengxian ~]# resize2fs /dev/shuaige/haha 300M #缩小300M
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/shuaige/haha to 307200 (1k) blocks.
The filesystem on /dev/shuaige/haha is now 307200 blocks long.
4.缩小（先通知系统内核自己想缩小逻辑卷，如果resize2fs命令执行后没有报错，系统允许了，再正式操作）
[root@xiudaochengxian ~]# lvreduce -L 300M /dev/shuaige/haha
WARNING: Reducing active logical volume to 300.00 MiB.
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce shuaige/haha? [y/n]: y
Size of logical volume shuaige/haha changed from 800.00 MiB (200 extents) to 300.00 MiB (75 extents).
Logical volume shuaige/haha successfully resized.
5.重新挂载文件系统并查看系统状态
[root@xiudaochengxian ~]# mount -a
[root@xiudaochengxian ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 17G 3.5G 14G 21% /
devtmpfs 1.9G 0 1.9G 0% /dev
tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs 1.9G 13M 1.9G 1% /run
tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/sr0 4.2G 4.2G 0 100% /media/cdrom
/dev/sda1 1014M 165M 850M 17% /boot
tmpfs 378M 4.0K 378M 1% /run/user/42
tmpfs 378M 24K 378M 1% /run/user/0
/dev/mapper/shuaige-haha 283M 2.1M 262M 1% /haha
删除逻辑卷
1.卸载文件系统
[root@xiudaochengxian ~]# umount /haha/
2.删除文件挂载信息
[root@xiudaochengxian ~]# vim /etc/fstab13 /dev/shuaige/haha /haha ext4 defaults 0 0
3.移除LVM逻辑卷
[root@xiudaochengxian ~]# lvremove /dev/shuaige/haha
Do you really want to remove active logical volume shuaige/haha? [y/n]: y
Logical volume "haha" successfully removed
4.删除卷组
[root@xiudaochengxian ~]# vgremove shuaige
Volume group "shuaige" successfully removed
5.让物理卷不再支持LVM技术
[root@xiudaochengxian ~]# pvremove /dev/sdb
Labels on physical volume "/dev/sdb" successfully wiped.
[root@xiudaochengxian ~]# pvremove /dev/sdc
Labels on physical volume "/dev/sdc" successfully wiped.
· 逻辑卷快照
LVM的快照卷功能类似于虚拟机软件的还原时间点功能
例：对某一个逻辑卷设备做一次快照，如果日后发现数据被改错了，就可以利用之前做好的快照卷进行覆盖还原LVM的快照卷功能有两个特点：
1.快照卷的容量必须等同于逻辑卷的容量
2.快照卷仅一次有效，一旦执行还原操作后则会被立即自动删除
1.创建快照卷
[root@xiudaochengxian ~]# cd /haha
[root@xiudaochengxian haha]# ls
lost+found
[root@xiudaochengxian haha]# cp -rf /etc/* ./ #复制一些文件到目录里
[root@xiudaochengxian haha]# lvcreate -L 300M -s -n SNAP /dev/shuaige/haha 创建快照卷
Logical volume "SNAP" created.
查看SNAP
[root@xiudaochengxian haha]# lvdisplay
--- Logical volume ---
LV Path /dev/shuaige/haha
LV Name haha
VG Name shuaige
LV UUID SKbcGd-DcP1-WJB9-pgQt-mt9e-ORgc-ZeA7xs
LV Write Access read/write
LV Creation host, time xiudaochengxian, 2021-11-01 16:42:57 +0800
LV snapshot status source of
SNAP [active]
LV Status available
# open 1
LV Size 300.00 MiB
Current LE 75
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:0
--- Logical volume ---
LV Path /dev/shuaige/SNAP
LV Name SNAP
VG Name shuaige
LV UUID yZHVcw-wvb1-mVft-ZKGd-XNai-32xW-S4OPD1
LV Write Access read/write
LV Creation host, time xiudaochengxian, 2021-11-05 11:02:46 +0800
LV snapshot status active destination for haha
LV Status available
# open 0
LV Size 300.00 MiB
Current LE 75
COW-table size 300.00 MiB
COW-table LE 75
Allocated to snapshot 0.01%
Snapshot chunk size 4.00 KiB
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:3
2.检验SNAP快照效果
[root@xiudaochengxian haha]# rm -rf * #删除目录下所有文件
[root@xiudaochengxian haha]# ls
[root@xiudaochengxian haha]#
[root@xiudaochengxian haha]# cd
[root@xiudaochengxian ~]# umount /haha #卸载挂载的目录
[root@xiudaochengxian ~]# lvconvert --merge /dev/shuaige/SNAP #恢复数据
Merging of volume shuaige/SNAP started.
shuaige/haha: Merged: 100.00%
[root@xiudaochengxian ~]# mount -a #查看文件是否恢复
[root@xiudaochengxian ~]# cd /haha/
[root@xiudaochengxian haha]# ls
abrt maven
adjtime mcelog
aliases mime.types
aliases.db mke2fs.conf
alsa modprobe.d
alternatives modules-load.d
anacrontab motd
asound.conf mtab
at.deny mtools.conf
audisp multipath
audit my.cnf
avahi my.cnf.d
bash_completion.d nanorc
bashrc netconfig
binfmt.d NetworkManager
bluetooth networks
.......